consulate in benghazi, libya. the attackers were muslim protesters apparently angry about an internet film produced in the united states that rid kulz the prophet muhammad. also among the four killed was sean smith, a foreign service information officer. the other two americans have not yet been identified because the state department is still notifying their families. cbs news national security correspondent david martin has been looking into all this at the pentagon. david? >> scott, good morning. u.s. officials do not believe these killings were the work of that mob that was demonstrating at the u.s. consulate. u.s. officials believe that within that mob, there were heavily armed militants who were, if you will, using the demonstration as a cover to get into that consulate and then take as much revenge as they could on americans. now, whether they were seeking revenge for this anti-muslim video or whether they were simply trying to kill americans on the anniversary of 9/11 is still unclear. >> david, thank you.